Quantitative and qualitative determination of natural occuring regulatory t cells in blood and bronchoalveolar lavage fluid of patients with pulmonary sarcoidosis and healthy volunteers.

Pulmonary sarcoidosis is a chronic inflammatory disorder of unknown aetiology,
characterized by non-caseating granulomas and compartmentalized inflammation
with accumulation of activated CD4+ lymphocytes in the lung [1,2]. Untill now
an antigen at which the inflammation is directed, has not been discovered
although a possible role of bacteria in saroidosis has been extensively
studied. Especially Gram-positive and intracellular bacteria, such as
mycobacteria and propionibacteria, have been suggested to play a role in the
aetiology of sarcoidosis [3-5].
Persistant antigen stimulation may result in chronic inflammation and can cause
immune pathology to surrounding lung tissue. The balance between protective and
immunopathological effects of the Th1-type cellular immune response may
determine a good prognosis in patients with sarcoidosis, ie Löfgren syndrome or
a chronic manifestation with severe lung fibrosis and destruction of lung
tissue.

It has been well documented that a unique population of lymphocytes, regulatory
T cells, are responsible for suppression of cellular immune responses. In
addition to cell-intrinsic peripheral tolerance mechanisms such as anergy
induction and peripheral deletion, CD4+CD25bright Tregs play indispensible
roles in the maintaince of natural tolerance, in averting autoimmune responses,
as well as controlling inflammatory reactions [6-12].
Regulatory T cells suppress both Th1- and Th2-mediated immune responses in such
a way that suficient immunity remains for clearing infectious agents while
unwanted immunopathology is prevented. In case of shortage of regulatory T
cells the potential amplitude of Th1 and Th2 responses is increased resulting
in excessive T cell immunity as associated with autoimmune disease, asthma
and allergy, allograft rejection, and some cases of early pregnancy
loss. Abundance of regulatory T cells, on the other hand, will reduce the
potential amplitude of Th1 and Th2 responses and therefore may prevent
adequate immunity to tumours and infectious diseases, but also effective
vaccination against infections [6,13].

In the past few years, intensive research has led to numerous publications
describing the role of Tregs in a variety of autoimmune or chronic inflammatory
diseases [14-19]. With respect to sarcoidosis, Planck et al 2003 [20] found an
increased percentage of peripheral blood CD4+CDbright lymphocytes in patients
with active Löfgren syndrome compared to those with resolved disease and
healthy controls and increased CD4+CDbright lymphocytes in BAL compared to
healthy controls, suggesting accumulation of Tregs during inflammatory
conditions as a strategy for down-regulating harmful inflammatory reactions.
And very recently, an article published in february 2006, Miyara et al [21]
found an expanded but functional impaired global Treg subset in sarcoidosis
patients with active disease. Specifically, they demonstrate that CD4+CDbright
cells isolated from the peripheral blood of patients with active sarcoidosis
can suppress the responder CD4+ T cell proliferative response but not the
secretion of inflammatory cytokines TNFa and IFNg.

While both studies point towards an explicit role of Tregs in active disease
compared to resolved disease or healthy controls, differences in Treg
pupulations between acute and chronic manifestations of sarcoidosis, associated
with specific clinical and radiogical characteristics, are not described.

As mentioned above, an insufficient Treg populatin (in number or functional
inadequate), may lead to chronic inflammation in sarcoidosis patients and
finally to irreversible scar tissue or fibrosis.

We hypothesise that regulatory T cells are increased in patients with
sarcoidosis and that patients with Löfgren syndrome have a distinct Treg
lymphocyte population compared to sarcoidosis patients with chronic
manifestations. Phenotypical analysis of Treg cells from peripheral blood and
BAL as well as functional ex vivo stimulation assays will elucidate the role of
Tregs in sarcoidosis, in particular their involvement in chronic disease
course.



References

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The primary goal of this research is to characterize the regulatory Treg
population in peripheral blood and bronchoalveolar lavage in patients with
sarcoidosis compared to healthy controls. What is the frequency of these cells,
what is the phenetype of these cells and are these cells functional competent.
The secundary goal is the comparison between patients with an acute form of
sarcoidosis, i.e. Löfgren syndrome, and patients with chronic manifestations of
sarcoidosis. The hypothesis is that the latter patient group has a deviant Treg
population.

Answers to these questions give insight to the immune (patho) physiology of the
disease and possible therapeutical opportunities to treat the disease.

The design of this study is observational. Bronchoalveolar Lavage and
venapuncture are once performed in included patients for diagnostic purposes,
extra blood is drawn from existing venapuncture.

The BAL and venipuncture are performed for diagnostic puposes. Risks of drawing
extra blood from existing venapuncture are minimal.
This research will benefit future patients.